One of the best ways that I have found to reinforce my own studying is by finding a community at my school that is interested in actuarial science, and helping to teach others the material I am learning myself. To be able to teach something, you really need to understand it completely, and knowing I have a deadline coming up for a presentation that I am giving is one of the best motivators for studying and forcing myself to really understand exam material.
Even if you do not feel comfortable teaching others material directly, simply finding other students that are interested in actuarial science gives you opportunities to improve your own knowledge of exam material. Group study sessions can be valuable, but even more valuable is the ability to talk to someone if you are having difficulty with a certain topic or need help solving an exam question. These things can make a huge difference; I urge you to consider them if you are one of the many students who simply study for exams on their own.
Not everyone has a community where they have the opportunity to give presentations on exam material or participate in group study sessions, but everyone has people that they can talk to. If you do not have actuarial students that are nearby, try teaching exam material to a family member or friend. Certainly the material is complicated and might not be easily understood, but if you can get across some of the basic concepts of exam material to someone who knows nothing about actuarial science, it is likely that you have a strong grasp of the material yourself.
Everyone works a little differently when it comes to studying for exams, and it might be that you feel uncomfortable in group study sessions or teaching others material. I think you should do it anyways. It does not need to be, even should not be, your main method of studying. But actuaries need effective communication skills on the job and teaching complicated topics that are important to actuarial science while you are still a student, or at least participating in a group learning situation, can be a great way to help develop those skills. On top of that, it really is next to impossible to teach a topic that you do not fully understand, so forcing yourself to try teaching can be one more way you can help motivate yourself to put in those study hours. Try it out; it might make a meaningful difference.